JP3088528B2 - Micro-liquid flow rate detection element and micro-liquid supply device using the element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow cytometer used for blood tests and the like, a minute liquid flow rate detecting element used for sending a minute liquid such as an ink jet recording head for ejecting a liquid, and a minute liquid. It relates to a supply device.

[0002]

2. Description of the Related Art At present, an industrial field for handling fine liquids is increasing. For example, ink jet recording, in which ink (liquid) is ejected and adhered onto a recording medium such as paper to perform recording, aims at high-definition images. Therefore, the diameter of the nozzle (small tube) is as fine as several tens of μm.
As the thin tubes become finer, the ejection device that ejects ink and the variation in the diameter of the thin tubes directly affect the image at the time of printing. Therefore, the injection device and the thin tube are formed by a precise processing method using photolithography. There is a blood test system in the field of handling other minute liquids. FIG.
Shows the flow chamber of the flow cytometer used in this blood test system. Transfer liquid inflow pipe 3 of flow chamber 1 formed by processing glass
When the transfer liquid (not shown) is introduced into the flow chamber 1 from the nozzle, the suction pressure generated by the flow of the transfer liquid causes the pressure in the nozzle 4 to be reduced, whereby the diluted blood flows from the sample inflow pipe 2 into the chamber 1. Nozzle 4
Through the capillary 5. In order to perform a blood test with higher precision, it is necessary to form a flow chamber and a thin tube with finer and higher precision, and an attempt has been made to fabricate a chamber on a glass substrate using photolithography in the same manner as ink jet (R .Miyake, "A Development of
Micro Sheath Flow Chamber ", Proceeding IEEE Micro
Electro Mechanical Systems, pp 265-270, 1991).

[0003] As the diameter of these thin tubes becomes finer, the flow rate of the liquid depends on the dispersion of the thin tubes and the supply control accuracy of the liquid supply pump. For this reason, a method of producing a thin tube by photolithography and producing a liquid supply pump for transporting the liquid with high reproducibility and high precision, or providing a mechanism for adjusting the pressure applied to the transport liquid with high precision, etc. Has been taken.

However, when a liquid flows through a thin tube having a diameter of 0.1 mm or less, the viscosity of the liquid is affected in addition to the supply control accuracy of the liquid supply pump. For this reason, it is necessary to precisely control the viscosity and the liquid temperature of the liquid. Conventionally, the liquid management and adjustment mechanism is provided not in the thin tube but in the process before the liquid flows into the thin tube such as the liquid tank, and the flow rate in the thin tube that you really want to detect and control cannot be directly measured, and it is treated as a black box Had been. Furthermore, when trying to multiply thin tubes, the flow rate in the thin tubes has a fraction due to the above control accuracy for each thin tube, and in order to improve the stability of the flow speed, the thin tubes and pumps are reproducible with high accuracy. It had to be made well.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a minute liquid flow rate detecting element capable of directly detecting a minute liquid flow simply and accurately, and a minute liquid. To provide a supply device.

[0006]

According to the present invention, there is provided a microfluidic flow rate detecting element for detecting a flow velocity of a fluid, comprising: a second substrate;
A pressure detecting portion provided on the second substrate; and a first tube forming groove for forming the narrow tube space together with the second substrate so that the pressure detecting portion can be located in the narrow tube space.
And a pressure sensor, wherein the pressure detector has a piezoresistive element provided in contact with a thin film membrane provided separately from the second substrate via a gap. Related to the element. At this time, the pressure detection unit can detect a pressure change based on the amount of deflection of the membrane. Further, the present invention provides a microfluidic flow rate detecting element for detecting a flow velocity of a fluid, wherein a second substrate, a pressure detecting portion provided on the second substrate, and the pressure detecting portion can be located in a narrow tube space. A first substrate formed with a groove for forming a narrow tube that forms the narrow tube space together with the second substrate, wherein the pressure detection unit has a portion separated from the second substrate; The present invention relates to a microfluidic flow rate detecting element having a piezoelectric thin film having a shape. The piezoelectric thin film may be provided with an electrode for detecting its piezoelectric effect. Further, the pressure detecting unit can detect a pressure change based on a bending amount of the cantilever-shaped piezoelectric thin film.

At least one of the first and second substrates may be formed of a glass plate, and at least one of the first and second substrates may be formed of single crystal silicon. Further, the depth of the capillary space can be set to 100 μm or less.

Further, the present invention comprises the element, a liquid transfer section formed on the inner wall of the thin tube section of the element, and a control section, wherein the detection section detects the pressure of the liquid in the thin tube and sends the liquid to the liquid transfer section. The feed amount is controlled by feedback, which includes that the liquid feed portion is formed of a thin film resistor.

[0009]

The minute liquid flow rate detecting element having the above configuration is
The flow rate of the liquid in the thin tube is directly detected as the flow rate pressure, and the liquid supply amount of the liquid supply pump (liquid transfer unit) is adjusted.

[0010]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is an exploded perspective view showing a minute liquid flow rate detecting element 100, in which 12 is a second substrate made of silicon.

On the upper surface of the second substrate 12, two extraction electrodes 18 and 18 'are formed by evaporating aluminum, and a piezoresistive element is provided as the pressure detecting section 10.

Reference numeral 13 denotes a first substrate made of glass, on the lower surface of which is formed a groove 11a for forming a thin tube. As a method for forming the groove 11a in the first substrate 13 made of glass, photosensitive glass is used for photolithography. Further, the glass can be removed by etching to a desired groove depth with hydrofluoric acid. As another method, for example, a resist may be used as a groove by applying a resist to the first substrate 13 made of glass or the second substrate 12 made of silicon, and developing and solidifying the resist by a photolithography process. The groove 11a can also be formed by anodically bonding a silicon substrate formed by etching a pattern of a thin tube to a glass substrate.

By bonding the two substrates 12 and 13 to each other with an adhesive, a thin tube 11 to be described later is formed by the substrate 12 and the groove 11a, and the pressure detecting unit 10 is positioned in the thin tube 11. Things.

FIG. 2 shows a manufacturing process of a pressure detecting section 10 for detecting a flow velocity of a liquid, which is a main part of the liquid flow control element, according to a micromachining technique (S. Sugiyama, "S.
ilicon Integrated Pressure Sensors ", Proc. of 2nd
International, Forum ASCI & Trans. Tech., Pp5-12, 1
989).

As shown in FIG. 2A, a sacrificial layer 7 made of a silicon oxide film is formed on a second substrate 12 made of silicon. Next, an insulating layer 15 made of a silicon nitride film is formed to cover the upper surface of the sacrificial layer 7 and the upper surface of the substrate 12.
Further, a p-type piezoresistive element 16 is formed thereon.
In the method of forming the piezoresistive element, a polysilicon layer is formed on the insulating layer 15 and boron ions are implanted into the polysilicon layer.

Next, as shown in FIG.
An etch hole 8 is formed in a part of the hole 5 by reactive ion etching using CF ₄ gas, and the sacrifice layer 7 is etched and removed with hydrofluoric acid or an aqueous solution of ammonium fluoride through the etch hole 8 to form the void portion 14. Form.

After that, as shown in FIG. 2C, a protective layer 17 made of a silicon nitride film is formed by a plasma CVD method so as to cover the piezoresistive element 16 and the insulating layer 15.
Thereby, the etch hole 8 is closed and the piezoresistive element 1 is closed.
6 is protected. In this case, the portion of the insulating layer 15 above the void portion 14 forms a flexible membrane 27.

Next, as shown in FIG.
The extraction hole 6 is formed in the electrode 7, and then the signal extraction electrode 18 is formed by aluminum evaporation. Finally the second
By joining the first substrate 13 having the groove 11 a formed on the substrate 12, the minute liquid flow detecting element 100 having the pressure detecting section 10 formed in the narrow tube 11 is obtained.

FIG. 3 is an overall configuration diagram of the micro liquid supply device. The liquid is supplied from the liquid tank to the liquid supply pump (liquid transfer unit 21) through the liquid introduction pipe 20. The pump driving circuit 22 controls the flow rate of the liquid while controlling the thin tube 11 shown in FIG.
Send liquid to The flow velocity of the liquid flowing through the thin tube 11 is detected as a change in resistance of the piezoresistive element due to the deformation of the membrane of the pressure detector 10 shown in FIG. The control amount is fed back to the pump drive circuit 22 by the CPU 24 to adjust the flow rate of the liquid. Although it was difficult to directly detect the fluid flow velocity in the thin tube with the conventional flow cytometer, the present invention makes it possible to precisely adjust the liquid transfer speed.

FIG. 4 is a diagram showing the configuration of the pressure detector 10 'of the second embodiment. The extraction electrodes 18 and 18 ′ and the piezoelectric thin film 19 are formed on the substrate 12 which constitutes a part of the thin tube 11.
Is formed. A tungsten-titanium alloy serving as a sacrificial layer (not shown) is formed on the silicon substrate 12 below the cantilever in the figure, and then Al is formed and patterned to form an extraction electrode 18. A piezoelectric thin film 19 made of ZnO is vacuum-deposited on the extraction electrode 18 by a sputtering method, patterned into a cantilever shape, and Al is deposited and patterned to form an extraction electrode 18 '. Thereafter, the sacrificial layer of tungsten-titanium is removed by etching using a hydrogen peroxide solution to obtain a pressure detector 10 'having a cantilever shape. The thin tube 11 is formed by the same method as in the first embodiment.

The cantilever pressure detector 10 ′, which is a cantilever, is bent by the flow velocity pressure of the liquid passing through the thin tube 11, and the flow rate is increased by generating a voltage difference between both ends of the extraction electrodes 18, 18 ′ of the piezoelectric film 19. Detect pressure.

By using the liquid flow rate detector 10 'of the second embodiment to constitute the micro liquid supply device shown in FIG. 3, it is possible to adjust the flow rate of the liquid in the same manner as in the first embodiment. Become.

Although a silicon substrate is used in both of the above embodiments, a similar liquid flow velocity detecting unit can be formed using quartz, glass, or the like. The piezoelectric body may be any material having a piezoelectric effect, such as aluminum nitride, tantalum pentoxide, lead titanate, barium titanate and the like. Known piezoresistors can be used, and various modifications may be made without departing from the scope of the present invention.

FIG. 5 shows the configuration of an ink jet recording head which is a minute liquid supply device according to the third embodiment. FIG. 5 shows only one of the ink jet recording heads, and the present configuration is actually formed as a multiple. A liquid transfer unit (liquid supply pump), a pressure detection unit, and a thin tube are integrated on a substrate. A heater 25 made of a thin film resistor is used as a liquid transporting unit. By heating the heater 25, a bubble is formed in the ink 26 and the ink is ejected from the nozzle 4. At this time, pressure is applied to the gap portion 14 provided close to the same substrate due to the flow of the liquid, and the membrane 27 made of an insulating layer is deformed, the resistance of the piezoresistive element 16 provided on the membrane changes, and ink Detect the flow rate. The ejection amount of ink can be detected by reading the signal of the flow velocity detected in this manner.

With such a configuration, the amount of ink ejected from the recording heads shown in FIG. 5 arranged in multiples can be detected for each head, and when one head is clogged, the ink is ejected by another head. It becomes possible to substitute. Further, it is also possible to provide an ink jet recording head having uniform print quality by feedback-controlling the electric power applied for heating the heater of each head.

[0027]

As described above, the minute liquid flow rate detecting element according to the present invention can detect a minute flow rate, and the minute liquid supply device using the same can detect the flow velocity pressure to flow the liquid accurately. Becomes

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing a configuration of a minute liquid flow rate detecting element according to an embodiment of the present invention.

FIG. 2 is an explanatory view showing a manufacturing process of the device of FIG.

FIG. 3 is a block diagram showing an example of a micro liquid supply device incorporating the element of FIG.

FIG. 4 is a schematic configuration diagram showing a minute liquid flow rate detection element according to another embodiment of the present invention.

FIG. 5 is a schematic configuration diagram showing an ink jet recording head according to still another embodiment of the present invention.

FIG. 6 is a schematic configuration diagram showing a flow chamber of a flow cytometer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Flow chamber 2 Sample inflow pipe 3 Conveying liquid inflow pipe 4 Nozzle 5 Narrow tube 6 Extraction hole 7 Sacrificial layer 8 Etch hole 10 Pressure detection unit 10 'Pressure detection unit 11 Small tube 11a Groove 12 Second substrate 13 First substrate 14 Void DESCRIPTION OF SYMBOLS 15 Insulating layer 16 Piezoresistive element 17 Protective layer 18 Extraction electrode 18 'Extraction electrode 19 Piezoelectric thin film 20 Liquid introduction pipe 21 Liquid transport section 22 Pump drive circuit 23 Flow velocity detection circuit 24 CPU 25 Heater 26 Ink 27 Membrane 100 Micro liquid flow rate detection element

Claims (10)

(57) [Claims] 1. A microfluidic flow rate detecting element for detecting a flow velocity of a fluid, comprising: a second substrate; a pressure detecting unit provided on the second substrate; and a pressure detecting unit disposed in the capillary space. A first substrate on which a capillary forming groove for forming the capillary space is formed together with a second substrate, wherein the pressure detecting unit is provided separately from the second substrate via a gap portion A microfluidic flow rate detecting element comprising a piezoresistive element provided in contact with a membrane. 2. The element according to claim 1, wherein the pressure detector is capable of detecting a change in pressure based on a deflection amount of the membrane. 3. A microfluidic flow rate detecting element for detecting a flow rate of a fluid, comprising: a second substrate; a pressure detecting unit provided on the second substrate; and a pressure detecting unit disposed in the narrow tube space. A first substrate on which a capillary forming groove for forming the capillary space is formed together with a second substrate, wherein the pressure detecting portion has a cantilever shape having a portion separated from the second substrate. A microfluidic flow rate detecting element comprising the piezoelectric thin film of (1). 4. The element according to claim 3, wherein said piezoelectric thin film is provided with an electrode for detecting a piezoelectric effect thereof. 5. The element according to claim 3, wherein the pressure detector is capable of detecting a change in pressure based on an amount of bending of the cantilever-shaped piezoelectric thin film. 6. The device according to claim 1, wherein at least one of the first and second substrates is made of a glass plate. 7. The device according to claim 1, wherein at least one of the first and second substrates is made of single crystal silicon. 8. The device according to claim 1, wherein a depth of the capillary space is 100 μm or less. 9. A liquid transporter comprising: the element according to claim 1; a liquid transport unit formed on an inner wall of the capillary space of the element; and a control unit, wherein the pressure of the liquid in the capillary space is detected by a detector and the liquid is transported. A minute liquid supply device that controls a liquid conveyance amount by feeding back to a unit. 10. The apparatus according to claim 9, wherein the liquid transport section comprises a thin film resistor.